The present invention relates generally to soap bars and, more particularly, to production of clear soap bars prepared from sodium cocoyl isethionate.
Soaps have been traditionally prepared from fatty acids, such as tallow class fats, that have surface-active agent, or surfactant, qualities, namely simultaneous solubility in both aqueous and organic phases. This dual nature allows surfactants to clean dirt and oil from surfaces and produce lather. The primary surfactants used in soap bars are sodium salts of fatty acids.
Formulation of bar soaps have become increasingly complicated because of changes in bathing habits of consumers and emphasis on marketability of bar soaps to such customers. For example, because consumers bathe more frequently than in the past, milder soaps have been formulated. Performance of bar soaps are measured by lather, wet cracking, firmness and rinsability in addition to mildness to skin. To improve the performance of bar soaps and provide additional consumer benefits, a variety of additives may be formulated into soap bars including free fatty acids, glycerol, colorants, dyes, pigments, fragrance, chelants, antioxidants, mildness and skin additives, antimicrobial agents and synthetic surfactants.
Synthetic surfactants commonly have lower sensitivity to water hardness which results in a bar soap formulation having improved rinsing, lathering and general xe2x80x9cfeel to skinxe2x80x9d. Anionic class surfactants, such as sodium cocoyl isethionate (SCI), are commonly used synthetic surfactants in bar soap formulation. SCI is a milder surfactant but soap bars incorporating SCI typically cost more than simple soaps.
Recently, clear or transparent soap bars have become increasingly popular among consumers. For example, clear soap bars are aesthetically pleasing to a consumer""s eyes while also providing cleansing properties commonly associated with opaque or translucent soap bars. Clear soap bars have been prepared from SCI, but only SCI that had been prepared using an organic acid catalyst yielded bars of good clarity. Use of organic acid catalysts can be problematic in the production of SCI, leading to either longer reaction times or lower activity levels than those achievable with inorganic catalysts, making the SCI more expensive on a per pound active basis.
What is therefore needed is a clear soap bar that can be prepared from SCI that contains/is produced using inorganic catalysts which is more economical and faster than SCI produced using organic acid catalysts. Further needed is a clear soap bar formulation based on metal catalyzed SCI and method of producing the clear soap bar.
The present invention is a clear soap bar formulation based on sodium cocoyl isethionate (SCI) and method for producing the clear soap bar. The invented soap bar formulation uses a SCI prepared with zinc catalyst to promote faster and more economical production of SCI. In a preferred embodiment, tetrasodium ethylene diaminetetraacetic acid (EDTA) is added to the soap bar formulation, depending on the zinc content of the formulation, to eliminate opacity and produce a substantially clear soap bar. Addition of EDTA to the soap bar formulation at a ratio to zinc content is preferably from about 1:1 to about 5:1 by weight. The invented clear soap bar formulation may also contain one or more common soap bar ancillary agents including but not limited to foam stabilizers, humectants, emollients, and fragrances.
In one embodiment, the invented clear soap bar is formed from a preliminary mixture of propylene glycol, sorbitol, sodium lauryl ether sulfate (SLES), glycerin, water, stearic acid and myristic acid. The preliminary mixture is stirred and heated, and sodium hydroxide is added for saponification of the fatty acids to form soap. The resulting mixture is stirred until homogeneous, and EDTA is added. The mixture is stirred again until homogeneous. SCI is then added, and the mixture is stirred until substantially clear. The mixture is then allowed to sit without stirring for a period of time, in order to allow air bubbles to rise to the top of the vessel. The mixture is poured into molds and allowed to cool undisturbed.
The method for producing the clear soap bar includes the steps of: producing a mixture of propylene glycol, sorbitol, SLES, glycerin, water, stearic acid and myristic acid in a vessel; heating the mixture while stirring to a temperature from about 45xc2x0 C. to about 65xc2x0 C.; when the mixture is completely molten, slowly adding NaOH while maintaining a temperature of the mixture from bout 65xc2x0 C. to about 75xc2x0 C.; stirring the mixture until it is substantially homogenized; adding EDTA to the mixture at a quantity based on the zinc content of the SCI of about 1:1 to about 5:1 by weight; stirring the mixture until the mixture is substantially homogenized; adding SCI and stirring until the mixture is substantially homogenized and the SCI is dissolved at a temperature from about 65xc2x0 C. to about 75xc2x0 C. and stirring for about 60 minutes to about 120 minutes; allowing air bubbles in the mixture to rise to the surface; pouring the mixture into molds at a temperature from about 65xc2x0 C. to about 75xc2x0 C.; and, cooling the mixture undisturbed.
The present invention is a clear soap bar based on sodium cocoyl isethionate (SCI) that is more economical to produce and is processed faster than conventional soap bars based on SCI. Further, the present invention is a clear soap bar based on SCI where the SCI does not require production from an organic catalyst. The invented clear soap bar is milder than traditional soap and can be used on a regular basis by individuals. The invented clear soap bar includes a primary mixture of propylene glycol, sorbitol, an anionic surfactant, glycerin, water, stearic acid and myristic acid. Sodium hydroxide, a chelating agent, and SCI are added to the primary mixture in accordance with the invented process described in greater detail hereinafter.
The clear soap bar formulation may optionally include common soap bar ancillary agents including but not limited to foam stabilizers, humectants, emollients, antibacterial agents and fragrances. Examples of foam stabilizers include alkyl monoethanolamides, alkyl diethanolamides, acyl sarcosinates, acyl taurates, acyl isethionates, acyl lactates, alkyl amine oxides, alkyl betaines, alkyl ether carboxylates, acyl glutamates and mixtures thereof. Examples of humectants include glycerine, propylene glycol, butylene glycol, polyethylene glycol and mixtures thereof. Examples of emollients include mineral oil, vegetable oil, silicone oils, synthetic and semisynthetic emollient esters and mixtures thereof.
Ethylene diaminetetraacetic acid (EDTA) is preferably used as a chelating agent. Examples of alternative chelating agents include pentasodium diethylenetriamine pentaacetic acid (DTPA), sodium etidronate (EDHP) and citric acid. The clear soap bar may further include mildness and skin additives such as lanolin, vitamin E, aloe vera gel, and panthenol.
In one embodiment, the invented clear soap bar is formed from a preliminary mixture of propylene glycol, sorbitol, an anionic surfactant such as sodium lauryl ethyl sulfate (SLES), glycerin, water, stearic acid and myristic acid. The preliminary mixture is mixed and heated, and sodium hydroxide is added for saponification of the fatty acids to form soap. The resulting mixture is stirred until homogeneous, and a chelating agent, such as EDTA, is added. The mixture is stirred again until homogeneous. SCI is then added, the mixture is stirred for a period until the mixture is substantially clear with an additional period from about 1 to about 2 hours before stirring is ceased, and the mixture is allowed to settle. The processed mixture is poured into molds and cooled undisturbed.
The following Table I is a preferred embodiment of components and amounts of the present invention:
The method for producing the clear soap bar includes the steps of: producing a soap bar mixture of propylene glycol, sorbitol, an anionic surfactant such as SLES, glycerin, water, stearic acid and myristic acid (Table 1, component A) in a vessel; heating the mixture while stirring to a temperature from about 45xc2x0 C. to about 65xc2x0 C.; when the mixture is completely molten, slowly adding NaOH (Table 1, component B) while maintaining a temperature of the mixture from about 65xc2x0 C. to about 75xc2x0 C.; stirring until the mixture is substantially homogenized; adding EDTA (Table 1, component C) to the mixture at a quantity of about 1:1 to about 5:1 by weight based on the quantity of metal catalyst (e.g., zinc content) in SCI; stirring the mixture until the mixture is substantially homogenized; adding SCI (Hostapon(copyright) SCI 85 manufactured by Clariant Corporation, Charlotte, N.C.) (Table 1, component D) and stirring until the mixture is substantially clear and homogenized and the SCI is dissolved at a temperature from about 65xc2x0 C. to about 75xc2x0 C.; adding sodium laureth-13-carboxylate (Sandopan(copyright) LS24N manufactured by Clariant Corporation, Charlotte, N.C. (Table 1, component D) and stirring until the mixture is homogenized; adding triethanol amine (TEA) (Table 1, component E) and stirring for about 60 minutes to about 120 minutes; stopping agitation and allowing air bubbles in the mixture to rise to the surface; pouring the mixture into molds at a temperature from about 65xc2x0 C. to about 75xc2x0 C.; and, cooling the mixture undisturbed.
In a preferred embodiment, all components of A are mixed in a vessel and heated to a temperature from about 45xc2x0 C. to about 65xc2x0 C. When the acids of component A are completely molten, NaOH is added very slowly, such as dropwise, to the mixture to control the exotherm during saponification to preferably at or below 70xc2x0 C.xc2x15xc2x0 C. The mixture is mixed well at this temperature until homogeneous, and preferably mixed for about 30 minutes. EDTA is then added and the mixture is stirred for a few minutes until substantially homogeneous. SCI 85 is then added. The mixture is stirred until substantially clear at a temperature of about 70xc2x0 C.xc2x15xc2x0 C.; preferably for about 30 minutes when using powdered SCI 85 or about 60 minutes when using chip type SCI 85. Sodium Laureth-13-Carboxylate (Sandopan(copyright) LS24N) (D) is then added. The mixture is stirred until the mixture is homogenized. TEA (E) is then added and the mixture is stirred for a period of about 60 to about 120 minutes. The stirrer is turned off and air bubbles are allowed to rise to top of flask for a period of about 30 minutes. Then, the mixture is poured into molds at a temperature of about 70xc2x0 C.xc2x15xc2x0 C. The bars are allowed to cool undisturbed. When cooled, the bars are removed from the molds and wrapped.
In the aforementioned stirring after the addition of TEA, extended stir times at high temperature tend to discolor the final bars, and too short of a stir time yields bars that are slightly hazy. A two-hour stir after all ingredients have been added is sufficient to achieve the clarity desired without discoloration of the mixture under air. Chelating agents may be selected from the list including but not limited to ethylenediaminetetraacetic acid, disodium salt dihydrate, diammonium salt of ethylenediaminetetraacetic acid, Ethylenetriaminepentaacetic acid, DeQuest 2066 (AS# 22042-96-2), also known as phosphonic acid, [(phosphonomethyl)imino]bis[(2,1-ethanediylnitrilo) tetrakis(methylene)]tetrakis-sodium salt, and DTPA.
Alternative components include mild surfactants such as alkyl ether carboxylates, acyl glutamates, and amphoacetates. Ammonium hydroxide may be substituted for TEA. Other additives that are normal and customary for conventional soap bars may also be added to the soap bar mixture including but not limited to preservatives, dye, fragrance, vitamins (e.g., Vitamin E), botanical extracts, panthenol, and conditioning polymers.